1. Field of the Invention
The present invention relates to a process for preparing an absorbent structure by using an electric field for contacting a substantially neutrally charged material that is responsive to the electric field with a substrate and a disposable absorbent product, intended for the absorption of body fluids, prepared by the process.
2. Description of the Related Art
The use of hydrogel-forming polymeric materials, commonly known as superabsorbents, in disposable absorbent personal care products is known. A wide variety of materials has been described for use as hydrogel-forming polymeric materials in such personal care products. Such materials include natural-based materials such as agar, pectin, gums, carboxyalkyl starch, and carboxyalkyl cellulose; as well as synthetic materials such as polyacrylates, polyacrylamides, and hydrolyzed polyacrylonitrile.
Such superabsorbent materials are generally employed in absorbent products such as diapers, training pants, adult incontinence products, and feminine care products in order to increase the absorbent capacity of such products while reducing their overall bulk. Such superabsorbent materials are generally present in absorbent products in a fibrous matrix, such as a matrix of wood pulp fluff. A matrix of wood pulp fluff generally has an absorbent capacity of about 6 grams of liquid per gram of fluff. The superabsorbent materials described above generally have an absorbent capacity of at least about 10, preferably of about 20, and often of up to 50 times their weight of liquid. Clearly, incorporation of such superabsorbent materials in personal care products can reduce the overall bulk while increasing the absorbent capacity of such products.
Adhesive materials are also well known for use in disposable absorbent products. The adhesive material is typically used in the form of extruded lines, beads, or looping swirls of hot-melt adhesive to adhere different elements of the disposable absorbent product together. For example, a topsheet may be adhered to a backsheet, or a hydrogel-forming polymeric material may be constrained into a desired pattern by applying the hydrogel-forming polymeric material to adhesive material. A wide variety of materials has been described for use as adhesive materials in personal care products. Such materials include hot-melt adhesives, pressure-sensitive adhesives, or the like.
Various methods of incorporating a hydrogel-forming polymeric material or an adhesive material into a personal care product are known. One such method includes using a vacuum process to prepare a layered absorbent structure comprising a tissue web base and a hydrogel-forming polymeric material layer ideally located between two wood pulp fluff layers. A tissue web base moves over a continuous belt former, under vacuum, which attracts the desired wood pulp fluff and hydrogel-forming polymeric material from a forming chamber. In practice, however, turbulent air flow in the forming chamber typically results in an absorbent structure without a clear-cut layered structure wherein the hydrogel-forming polymeric material is somewhat randomly distributed within and across the wood pulp fluff layers.
Another vacuum process may be used to form an absorbent structure wherein the hydrogel-forming polymeric material is distributed within a porous tissue web base. Again, a tissue web base moves over a vacuum drum former which attracts the desired hydrogel-forming polymeric material from a forming chamber. The porosity of the tissue web base permits the absorbent material to become distributed within the tissue web base. However, the pore size distribution of the tissue web base typically overlaps the particle size distribution of the hydrogel-forming polymeric material particles. As such, an amount of the hydrogel-forming polymeric material will not be distributed within the tissue web base and will generally result in airborne hydrogel-forming polymeric material particles as the absorbent structure is further processed.
Another method of incorporating a hydrogel-forming polymeric material into a personal care product includes using a gravimetric process wherein the hydrogel-forming polymeric material is gravimetrically applied to a moving tissue web base with adhesive lines applied on the surface of the tissue web base. Typically, an amount of the hydrogel-forming polymeric material does not contact the adhesive lines so that such hydrogel-forming polymeric material is not adhered onto the tissue web base.
Known processes for incorporating a hydrogel-forming polymeric material or an adhesive material into a disposable absorbent product typically result in placement of an amount of the hydrogel-forming polymeric material or the adhesive material in undesired locations within the personal care product. Such an inefficient placement of the hydrogel-forming polymeric material or the adhesive material generally results in the use of more of the hydrogel-forming polymeric material or the adhesive material than would ideally be needed, thereby increasing the costs of manufacturing the personal care product. Additionally, the presence of the hydrogel-forming polymeric material or the adhesive material in undesired locations within the personal care product may negatively affect the designed performance of the personal care product. Furthermore, the inefficient placement of the hydrogel-forming polymeric material or the adhesive material often results in airborne hydrogel-forming polymeric material or adhesive material particles which can create housekeeping or cleanliness problems.